On Thu, Jan 29, 2009 at 2:17 PM, Greg KH <greg@xxxxxxxxx> wrote: > > > > On Wed, Jan 28, 2009 at 06:41:49PM -0600, Robert Hancock wrote: >> >> >> Greg KH wrote: >>> In looking at open(2), it says that O_DIRECT works on 512 byte boundries >>> with the 2.6 kernel release: >>> Under Linux 2.4, transfer sizes, and the alignment of the user >>> buffer and the file offset must all be multiples of the logical >>> block size of the file system. Under Linux 2.6, alignment to >>> 512-byte boundaries suffices. >>> However if you try to access an O_DIRECT opened file with a buffer that >>> is PAGE_SIZE aligned + 512 bytes, it fails in a bad way (wrong data is >>> read.) >>> Is this just a mistake in the documentation? Or am I reading it >>> incorrectly? >>> I have a test program that shows this if anyone wants it. >> >> Well, it sounds like a bug to me.. even if it's not supported, if you do >> such an access, surely the kernel should detect that and return EINVAL or >> something rather than reading corrupted data.. > > It doesn't. It says the read is successful, yet the data is not really > read into the buffer. Portions of it is, but not the amount we asked > for. Greg, Can you post your test program? Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
